Preparation and characterisation of TiO2 nanoparticle and titanate nanotube obtained from Ti-salt flocculated sludge with drinking water and seawater.

This study aimed to prepare and characterise titanium dioxide (TiO2) nanoparticles and titanate nanotubes produced from Ti-sat flocculated sludge with drinking water (DW) and seawater (SW). The Ti-salt flocculated sludge from DW and SW was incinerated at 600 degrees C to produce TiO2 nanoparticles. XRD results showed that the anatase TiO2 structure was predominant for TiO2 from DW (TiO2-DW) and TiO2 from SW (TiO2-SW), which were mainly doped with carbon atoms. Titanate nanotubes (tiNT) were obtained when TiO2-DW and TiO2-SW were hydrothermally treated with NaOH solution. Structure phase, shape, crystallisation and photocatalytic activity of tiNT were affected by the incineration temperature and the amount of sodium present in different tiNT. The tiNT doped with thiourea incinerated at 600 degrees C presented anatase phase, showing a high increase of the degree of crystallisation with nanotube-like structures. The photocatalytic activity of these photocatalysts was evaluated using photooxidation of gaseous acetaldehyde. Thiourea doped tiNT-DW and tiNT-SW showed similar photocatalytic activity compared to commercially available TiO2-P25 under UV light and indicated a photocatalytic activity under visible light.

Characterisation of titanium tetrachloride and titanium sulfate flocculation in wastewater treatment.

Flocculation with titanium tetrachloride (TiCl(4)) and titanium sulfate (Ti(SO(4))(2)) was investigated in terms of different coagulant doses, pH, turbidity, dissolved organic carbon (DOC), UV-254, colour, zeta potential, particle size and molecular weight distribution. The two coagulants were compared with the commonly used coagulants such as ferric chloride (FeCl(3)) and aluminium sulfate (Al(2)(SO(4))(3)). Titanium tetrachloride showed the highest turbidity removal, while titanium sulfate showed the highest reduction of UV-254 and colour at all pH values. The four coagulants were found to have similar organic removal up to 60-67% and resulted in similar organic removal in terms of various MW ranges. The decantability of the settled flocs was very high for titanium tetrachloride, titanium sulfate and ferric chloride compared with aluminium sulfate. The dominating coagulation mechanisms for titanium tetrachloride and titanium sulfate are still to be studied, since different precipitation reactions might take place at different pH even without flocculant addition. Titanium tetrachloride and titanium sulfate were found as effective new coagulants in wastewater treatment not only in terms of organic matter removal, but also in sludge reduction through the production of titanium dioxide.

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge.

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600°C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.

Preparation and characterisation of titanium dioxide (TiO2) and thiourea-doped titanate nanotubes prepared from wastewater flocculated sludge.

In this study, titanium (Ti), ferric (Fe) and aluminum (Al) salt flocculants were compared for their efficiency in treating wastewater collected from Sydney Olympic Park wastewater treatment plant by following the jar test procedure. Produced sludge from Ti-salt flocculation was dried and titanium dioxide (TiO2) nanoparticles were generated after the incineration of sludge produced from the Ti-salt flocculation of wastewater. Later on, titanate nanotubes were synthesized after TiO2 nanoparticles were hydrothermally treated with 10 N NaOH solution at 130 degrees C for 24 h. Titanate nanotubes were either acid or deionised water-washed, while thiourea-doping was employed to produce visible light-responsive nanotubes. Wastewater flocculation using Ti-salt was found to be as efficient as Fe and Al flocculation in terms of turbidity and DOC removal. XRD results showed that the anatase structure was predominant for TiO2 nanoparticles, while thiourea-doped titanate nanotubes only indicated anatase structure with an increased crystallinity after being crystallized at 600 degrees C. The photocatalytic activity of all photocatalysts was evaluated using the photooxidation of acetaldehyde. Thiourea-doped nanotubes showed a greater photocatalytic activity than as-prepared TiO2 nanoparticles, deionised water-washed, acid-washed titanate nanotubes and P25 under UV and visible light irradiation.